George BM

Baby Yoda: Lwxkm robbed? Forecast Discussion Thursday, May 30, 2024 10:58AM EDT Very strong and compact closed, cold-cored upper-level low will continue to move into and over the region as we go through the day. The cold front and rain/downpours associated with the front have moved east of the Bay leaving partial clearing and a rapidly cooling airmass aloft. This system is bringing in a record breaking cold-airmass for the end of May into our region. 500mb temperatures overhead will drop to around -32 to -33C w/ 850mb temps holding around -1 to -1.5C. Surface temperatures will climb a few degrees into the mid/upper 50sF for the afternoon. Now, for an airmass this cold, dewpoints will remain fairly high (around 40F or so) partially due to the compact nature of this low and higher dewpoints surrounding. This will lead to MLCAPE of 500+ J/kg by this afternoon which is, again, unusually high for an airmass this cold. In fact, the SPC has the area under a marginal risk of severe weather for today and are considering upgrading us to a slight (2 of 5) risk in the early afternoon update for wind and hail. Even during these late morning hours there are already some intense showers w/ a few lightning discharges mainly west of I-95 with some hail/graupel being reported. These will overspread the region, become more numerous and intensify as we go through the day. With the steep low and mid-level lapse rates in place combined w/ the instability in place as well as such cold thermodynamics, storms will be capable of 45-60mph wind gusts w/ torrential hailers looking likely. Some hailstones could exceed an inch in diameter (quarter-sized hail). The most intense storms could drop several inches of hail/graupel and briefly knock temps down into the upper 30s/lower 40s which will make travel treacherous for a time. By the evening the upper low will start moving to the east and showers and storms will, accordingly, taper off from west to east. Temperatures will fall into the upper 30s/lower 40s by dawn. Forecaster Wannabe: George BM Lwxkm: @Baby Yoda Good thing hail doesn't count as snowfall. While there may be graupel, I can't imagine that graupel as oppose to hail will be the main precip-type. I guess I can root for the three main local airports to get missed by today's hailers. RodSney: Nah. You've already been crowned. You won't have to forfeit your trophy. Now if some local airports get buried in graupel today causing someone else to have closer numbers, then I might make a trophy for them. But why is this even a thing we're discussing? It's practically June. Get with the program Mother Nature!

IAD has peaked at 91F so far breaking its daily record of 89F from 2017.

Just had quite a bit of dime to quarter-sized hail with that western Fairfax county storm.

Nonstop thunder in Herndon.

I noticed a fire blow up on satellite and radar SE of Fredericksburg, VA yesterday afternoon. I wonder if that could be the source?

Lol. A little part of me dies every time this occurs.

Question for those of you who saw totality in both 2017 and 2024. I notice that the width of totality with this eclipse was larger than it was for 2017. My question is: Did this eclipse's totality seem darker than 2017s?

Temp dropped from 74F to 69F at IAD.

Had two more brief bursts of frozen precip. One just ahead of the main line and one with the main line (rain/graupel) w/ 30+ mph wind gusts. Temp has dropped into the lower 40sF. IAD: 43/38

Now I just had a heavier shower (moderate downpour) w/ pea-sized hail/graupel.

Just had some brief ice pellets w/ a shower in Herndon around 15 minutes ago.

If it makes you feel better there've been many significant to record-breaking snows with the general pattern leading up to this eastern severe event in the western US mountains w/ Lake Tahoe and the California mountain peaks getting 10-15 feet of snow through the past week. Crazy for late April.

Verbatim... an elevated supercell/multicellular cluster w/ hail. Surface temps in the upper 40s locally at that time.

That line approaching Charleston, WV means business. It has a tornado warning box the size of some of the STW boxes we get here. Lots of kinks in the line.

Starting wet and possibly thundery.

Forecast Discussion Sunday, April 28, 2024 3:13PM EDT Much of the forecast area remains in a moderate (level 4 of 5) risk of severe weather from the Storm Prediction Center. The west to east frontal boundary remains draped over the region w/ the shortwave and associated area of low-pressure approaching from the west. Temperatures have risen into the mid-80s in most areas w/ unseasonably high low-level moisture (dewpoints into the lower 70sF). This combined with steep mid-level lapse rates (7.5-8C/km) has led to mlcape values exceeding 3,000 J/kg. There’s also a strong westerly flow aloft (700-400mb westerly winds of 60-70kts) contributing to the 65-80 kt effective bulk shear in place when combined with the easterly surface wind component. The unusually strong instability in place will allow storms to be able to take full advantage of this shear without getting ripped apart. Storms are expected to form within the next hour in the mountains west of 1-81 and move eastwards into the region as we go through the afternoon and evening. A few storms may also develop in the region in the general vicinity of the frontal boundary east of the mountains. With the shear in place supercells will be the primary storm-mode. Low-level shear will be high with effective SRH of 200-350m2/s2 commonplace. As a result, supercells could drop a couple of tornadoes, a tornado or two may become significant/long-track especially if it tracks right along the boundary. The strong instability in place combined with at least moderately strong downdraft CAPE (DCAPE: 900-1200J/kg) will also allow for severe downburst wind gusts. A few gusts may approach hurricane-force. With “fat-CAPE” particularly between the -10C and -30C level of the atmosphere, very large to giant hail may be common with these storms leading to extensive roof damage. Over time supercells may congeal into multicellular storm clusters, especially with additional storms that move in from the west allowing for areas to receive multiple rounds of severe storms through the evening. These storms will contain all hazards (tornadoes, severe wind, severe hail). This looks likely to be one of if not this region’s biggest severe weather event in more than a decade. Make sure you have a way to keep updated and get alerted with the severe weather going on, especially considering that storms will likely continue until after most peoples bedtime. Tornado Watch in effect until midnight EDT Monday, April 29, 2024 Hazards: A few tornadoes likely w/ a couple intense tornadoes possible Scattered large hail events w/ isolated very large hail events up to 3.5” diameter likely Widespread damaging winds w/ isolated significant gusts to 80 mph possible Watch Probs: Tor: 70/50 Wind: 80/50 Hail: 80/80 Average storm motion: 270/40

Woah. Kind of surprised to see us into the 15% risk for Tuesday and more surprised to see how far north the risk area extends (into southern PA) given how spring CAD setups usually play out. At a quick glance of the varsity models both the 0z CMC and 0z ECMWF had the warm front well to our south for Tuesday with only the GFS getting the warm front over us. I guess we'll see how this plays out. Now elevated convection/storms, on the other hand, I can see occurring to the north of the front. So, at the least, thunder/lightning is looking fairly likely for a good number of us on Tuesday. The SPC has better tools than we have at our disposal so it's definitely possible that they show something that the varsity models don't for Tuesday. As has been said, we'll see how this plays out and it's at least something severe-wise to track more locally.

A vibrant sunset will commence shortly.

SPC has that area in a 15% risk for that day. Slowly starting to warm up.

A number of birthdays in here today. Happy carrot cake/IPA day to those of you celebrating.

In the mountains to the west.

Starting to notice the smell of smoke and a slight "oranging" of the sun from the fires that have developed this afternoon in the mountains.

+17 at IAD.

IAD at 70/29.

I'd personally go with a completely cloudy totality. To see it go pitch black night in the middle of the afternoon is certainly quite the experience regardless of the weather... IMO at least.